1. Field of the Invention
The present invention relates generally to the fields of pharmacology and clinical medicine. More specifically, the present invention is directed to pharmaceutical compositions and methods for treatment of disease in humans that concern S-bucindolol.
2. Description of Related Art
The human endothelium has an essential role in regulating arterial blood flow and preserving normal vascular physiology. Important activities of the endothelium are mediated by the production of signaling molecules, especially nitric oxide (NO). Endothelial dysfunction, on the other hand, is linked to atherosclerosis and its clinical manifestations (coronary artery disease, heart failure) (Harrison et al., 1987; Liao, 1998; Oemar et al., 1998). Key risk factors for atherosclerosis, including dyslipidemia, smoking and diabetes, can be specifically linked to abnormalities in NO-mediated endothelial dilation (Harrison et al., 1987; Liao, 1998; Oemar et al., 1998). In addition, a reduction in NO bioavailability contributes to elevated vascular resistance and loss of sensitivity to stimuli of vasodilation, hallmark features of hypertension (Paniagua et al., 2001; Panza et al., 1990; Taddei et al., 1993).
Beyond vasodilation, NO has well-characterized vascular benefits, including inhibition of smooth muscle cell proliferation and migration, adhesion of leukocytes to the endothelium, and platelet aggregation (Harrison, 1997). In patients at higher risk for cardiovascular disease and its clinical consequences (e.g., African Americans), there is also evidence for reduced NO-mediated vasodilation associated with increased superoxide generation in endothelial cells (Campia et al., 2002; Kalinowski et al., 2004; Stein et al., 1997). Thus, agents that directly stimulate NO release may have important therapeutic advantages in the prevention and treatment of cardiovascular disease.
Hispanics are the largest and fastest-growing minority group in the United States, and Mexican Americans are the largest sub-group of Hispanics. Epidemiologic studies indicate that Mexicans have higher rates of coronary heart disease (CHD) risk equivalents, including type 2 diabetes mellitus, metabolic syndrome and some primary forms of dyslipidemia (Stem et al., 1991; Aguilar-Salinas et al., 2001; Aguilar-Salinas et al., 2003). By the age of 50, epidemiologic studies indicate that 28% of men and 21% of women in Mexico already exhibit some form of dyslipidemia (Aguilar-Salinas et al., 2001). In the San Antonio Heart Study, it was reported that after adjusting for age and gender, U.S.-born Mexican Americans were 1.4 times as likely to die of cardiovascular (CV) disease as non-Hispanic whites (Hunt et al., 2002). For cardiovascular disease, U.S.-born Mexican Americans were 1.7 times more likely to die from CVD and 1.9 times more likely to die from CHD than non-Hispanic whites (Hunt et al., 2002). To understand the basis for this enhanced risk, a recent study has identified genetic variants that confer higher susceptibility to dyslipidemia, but more studies are needed in this area (Aguilar-Salinas et al., 2003; Huerta-Vazquez et al., 2005). There are also well known environmental factors that contribute to higher risk in individual Mexican Americans, including a high-fat and high-calorie diet, tobacco use, alcohol consumption and sedentary lifestyle.
Hypertension is a risk factor that is less likely treated and controlled among Hispanics, as compared to the overall U.S. population. This was a key finding from the National Health and Nutrition Examination Surveys (NHANES) for 1999-2002. This report has identified racial/ethnic disparities in the awareness of, treatment for, and control of hypertension. NHANES is a stratified, multistage probability sample of the civilian, non-institutionalized U.S. population. During 1999-2002, the age-adjusted prevalence of hypertension in the study population was 28.6% (CI=26.8%-30.4%). The prevalence of hypertension increased with age, as expected, and was higher among women than men. Among adults with hypertension, the proportion aware of having this condition was 70.3% among non-Hispanic blacks, 62.9% among non-Hispanic whites, but only 49.8% among Mexican Americans. The age-adjusted proportion that reported treatment was 55.4% among non-Hispanic blacks, 48.6% among non-Hispanic whites, and only 34.9% among Mexican Americans. Only 29% of U.S. adults with hypertension had controlled BP levels (<140/90 mmHg). The proportion with controlled BP was similar among non-Hispanic blacks (29.8%) and non-Hispanic whites (29.8%) but substantially lower among Mexican Americans (17.3%). These findings indicate the challenge of effectively treating and controlling hypertension in the rapidly growing Hispanic and Mexican American population.
While epidemiologic studies indicate a higher risk of CV disease and lower BP control among Mexican Americans, the underlying pathophysiology is not well understood. Studies in other high-risk populations, such as African Americans, indicate that the higher risk is related to decreased responsiveness of conductance vessels to both endogenous and exogenous stimulants of NO, as compared with age-matched whites (Campia et al., 2002). To understand the basis for this difference, it was reported that there is lower bioavailability of NO from endothelium of black Americans, despite much higher levels of endothelial-dependent NO synthase (eNOS) (Kalinowski et al., 2004). The cellular basis for this paradox was the finding that excessive O2− generation by NAD(P)H-oxidase and uncoupled eNOS resulted in the loss of functional NO due to its reactivity with O2−, resulting in peroxynitrite (ONOO−) formation, a potent oxidant with the capacity to produce adverse biological effects (Kalinowski et al., 2004).
Thus, there is the need for improved therapy of hypertension and CV disease, particularly among racial groups where there is a high prevalence of these diseases.